Hydraulic fuse



Aug. 15, 1950 E. C. HARTLEY ETAL HYDRAULIC FUSE Fiied Nov. 22, 1944 7 ifZ5 Harry Car/"600 Patented Aug. 15, 1950 Emmett C, Hartley and Harry B.Carbon, Cleveland, Ohio, assignors to The Parker Appliance Compa y, nd,Ohio, a corporation of Qhio Application November 22, 1944, Serial No.564,640

. l The invention, of which the following is a detailed description,relates to a safety fuse for hydraulic pressure lines, sometimesreferred to as a hydraulic fuse. The general purpose of such devices isto cut off promptly the flow of,

pressure fluid, oil or the like, in piping where the latter is suddenlybroken. As an example it may be pointed out that hydraulic operatinglines are customarily used on airplanes for the control of Wings,ailerons, rudders, elevators and the like. In the event that the highpressure piping is broken it is necessary to seal the broken line toprevent loss of fluid and disturbances of the operating circuits.

One of the objects of our invention is to permit a normal flow of fluidunder pressure in an operating pipe circuit. It is also important thatnormal operation be not disturbed by momentary surges of abnormal orexcess flow and this is amply provided for by our improvement.

The object of our invention includes however means by which a continuedexcess of flow will result in a throttling action to restrict the volumeof fluid permitted to pass the valve or fuse.

A further object of our invention is to effect closure, stoppage orsealing off of the discharge side of the tubing immediately following abreak in that line and the loss of a material and predetermined quantityof fluid.

Another object of our invention is to restrict the loss of pressurefluid on the occasion of a rupture to a relatively constant smallquantity regardless of the range oi. pressure by which the fluid may bedelivered to the piping.

' It is'a still further object of our invention to calibrate thehydraulic fuse to a suitable amount determined by the volume for thedevice being actuated. Thus where the pressure fluid is being deliveredto the cylinder of a reciprocating pis ton, the volume of the cylindermay be used to determine the action of the fuse. For this purposethefuse may be calibrated to permit enough fluid to operate the cylindereven in the event of moderate leakage but to stop the flow after avolume has been delivered sufficient to fill the cylinder. Incidental tothe objects of our invention it is also intended to effect a promptreturn to the normal open position of the fuse when there is no furtherescape of the liquid, or when, under some operating conditions, thedirection of fluid pressure is reversed. a

.For purpose of illustration we have shown the preferred form of ourinvention in the accompanying drawings in which:

3 Claims. (01. f25114c) Figure 1 is a side elevation partly inlongitudiital section, of the improved fuse in its open post- Fig. 2 isan elevation of the inlet end;

Fig. 3 is a vertical section On the line 3-3 of Fig. 1;

Fig. 41s a vertical section on line 4-4 of Fig. 1, and

Fig. 5 is a side elevation, partly in longitudinal section of the fusein its closed position.

Generally speaking this hydraulic fuse forms part of a line of pipingthrough which fluid is conveyed under pressure for use in operating apiston or the like to produce reciprocating motion. The piping System isnot illustrated as it is conventional and forms no part of theinvention.

The fuse comprises a casing, housing or body member 5. This may beinterposed in the fluid pressure tubing by means of end fittings. Endfitting 7 is a cap which is bolted upon the discharge end of the bodymember by means of a flange 8 and appropriate bolts 9. The fitting issealed to the end of the body member 6 by means of a packing i0 which isseated in a periphera groove H of the fitting or end cap. The cap isinternally screw-threaded as at 12 and has a series of passageways l3connecting the central bore with the inner face of the cap. A circulargroove l4 connects with the inner ends of the assa eway it.

The inner face of the cap I is spaced from the opposite wall of the bodymember ii to receive a suitable valv seat I5. This is in the form of adisk of rubber or other elastic material which is not affected by thepressure fluid being used. The disk has a circular series of openings I6 opposite the groove E4. The thickness of the disk is such that it willnot be distorted but will main tain a substantially plane valve surface.By reason of the provisi nof groove it no care need be exercised tomaintain unrestricted flow between "the passageways is and the openingsto as 1111-.- restricted flow will be assured by the circular groove 54.The body 6 has a central bore in the form of a cylinder ll. One edge ofthis bore fits against the valve disk #5.

The opposite end of the valve cylinder l1 terminates in a dash-potchamber l8 0f substantially greater diameter and cross sectional area.This chamber extends towards the opposite ends of the member 6. At thepoint where the chamber i8 meets the cylinder H, the chamber isunder-cut to form an enlarged bore l9.

This end of the member 6 is closed by means of a cap or fittingzfl. Itis screw threaded 3 internally as at 2| and has a flange 22 by which itis bolted on the end of the body 6 with bolts 23.

The cap has a peripheral groove 24 accommodating a packing 25 by whichthe cap is sealed to the body.

A freely sliding valve member 26 is provided in the area of the cylinderl1 and the chamber IS. The valve 26 is generally cylindrical andprovides a sliding fit along the inner wall of the cylinder H. Theopposite end of the Valve has an out-- wardly directed flange 21 whichextends to the cylindrical wall of the chamber l8. On its outer edge theflange 21 is chamfered to reduce contact with the chamber surface. Atthe same time very close clearance is maintained between these twosurfaces being of the order of One to two thousandths of an inch. Thusthere is slight, if any leakage of pressure fluid around the flange. Aseries of metering openings 28 pass through the flange 2'! and connectthe chamber H? with the inlet end of the fuse.

'The valve 26 is held in normal open position with the flange 21 restingagainst the cap 2| by means of a coil spring 29. Check valves areprovided between the chamber l8 and the axial bore 3! of the valve 26.These check valves consist of one or more radially disposed recesses 3|.Each such recess terminates in a port 32 connecting with the bore 39. Aball valve 33' is loosely contained in the recess 3| and may sealthe'discharge to the bore 30 by fitting against the edge of the port 32.In order to prevent dislodgment of the ball valve 33 a split ringretainer 34 is carried in a peripheral groove around the outer surfaceof the valve 26.

Figure 1 shows the fuse in its open or normal operating position. Whenit is installed in a line of piping which is filled with fluid underpressure, the latter immediately fills not only the bore 30 but also thecylinder I, the dash-pot chamber I8 and the enlargement Hi. In thisposition the pressure is balanced between the chamber l8 and thecylinder I! so that the ball valves 33 are free to remain open. In thisposition and in the absence of the discharge of fluid pressure againstthe inlet of the fuse, there is no differential in the pressure at theinlet and the outlet.

When fluid is admitted under pressure to carry out the operating effectin the line beyond the outlet, it acts across the area of the front faceof the valve member 21 tending to move the valve toward the seat l5. Anadditional force for closing the valve is provided by the frictional andimpingement eifect of the moving fluid upon the valve 26 as it passestherethrough. The pressure fluid also acts across the rear face of thevalve which is opposed to the seat I5, tending to keep the valve open.The unit pressure acting on the rear face Will be less than that actingon the front face because there will be drop in pressure as the fluidpasses through the passage 39, and since the total area of the ports i6is greater than the area of the valve passage 30 there is no restrictionbeyond the passage 30 to cause a pressure rise.

Since the area of the rear face is smaller than the area of the frontface, and since the unit fluid pressure is greater upon the front facethan upon the rear face, and because of the frictional effect, the valve26 will move toward the seat against the action of the spring 29.

Closing movement of the valve is resisted by the dash pot, the pressureof the fluid within the dash pot chamber building up so as to close thecheck valve 32 and leaving only the metered open- 4 ings 28 throughwhich the fluid can escape from the dash pot chamber.

There is then no escape for the fluid under pressure in the chamberother than through the metering passageways 28 in the flange 21. It maybe stated at this point that the pressure of the fluid against theflange 2'! overcomes the coil spring 29 incidental to the discharge offluid through the passageways 28.

The valve 26 moves slowly at a predetermined rate of speed toward thevalve seat l5.

Normally the volume of pressure fluid desired to be used in theoperating circuit beyond the outlet will have passed beyond the outletbefore the valve 28 passes beyond the normal part of the chamber i8.Therefore the flow of pressure fluid is cut off before the valve 26completes its closing movement. Immediately a balance of pressuredevelops between the inner chamber of the fuse and the chamber l8resulting in the coil spring then driving the flange 2'! back to theopen position against the inlet fitting.

When however the flow through the outlet, due to leakage or rupture ofthe piping is excessive, then the valve 26 continues to move towards itsseat far enough to bring the flange 21 opposite the enlargement i9. Atthis point the discharge from the dash-pot and the enlargement |9 is nolonger restricted by the metering openings 28. Consequently the valve 26is brought against the valve seat |5 by a rapid movement such that theoutlets it are adequately closed.

It is to be noted that as soon as the pressure in the dash-pot and itsenlargement I9 is restored to that in the bore 30, the lower ball 33will fall away from the valve seat 32.

As long as the discharge line is ruptured, the pressure of the fluid inthe fuse will hold the valve 26 on its seat i5 and thus prevent furtherloss of fluid. This is illustrated in Figure 5.

As soon as operating conditions are restored in the discharge line thedifference in pressure no longer exists and the spring 29 brings thevalve back to its open position. This arrangement of 1 the valve permitsready adjustment for different operating conditions. Thus if thecylinder on the discharge end of the fuse varies from ten to twenty orforty cubic inches, a similar change in the number of the meteringopenings 28 is called for. These openings may be assumed to be onethirty-second of an inch in diameter. The flow through the fuse may varyfrom one to six gallons a minute. At the same time the pressure of thefluid may range from one hundred to one thou-' sand pounds per squareinch. It has been found that with a cylinder of forty cubic inches twosuch metering holes will be suflicient when used with a one-half inchtube line to cause the valve or fuse to close with loss of only fifteento eighteen fluid ounces of fluid.

Increasing the number of holes to three will accelerate the closing ofthe valve in case of rupture so that only from ten to fourteen fluidounces are lost regardless of variation in pres-' sure of from onehundred to one thousand pounds per square inch.

In like manner five metering holes in the flange check a loss of fluidof from five to eleven fluid ounces, over the same pressure arrangement.

From these results it is evident that regardless of the actual pressureor of the rate of flow of the fluid the fuse operates to close thebroken line after a relatively constant amount of fluid has passedtherethrough.

It is an important feature of the improvement that this throttling andsealing operation is effective only in one direction. Frequentlyreciprocation of the piston in the operating cylinder will drive thepressure fluid through the fuse in the reverse direction. Thus it willnot be delayed or impeded because the spring 29 will already have liftedthe valve from its seat and brought it into open position where it isinstantly available for use in throttling or limiting the flow of fluidwhen next passed through in the normal direction.

It will be evident that our invention has secured the above and otherincidental objects in an effective manner and that the arrangement isdurable, economical of manufacture and replacement. Various changes maybe made in minor details in arrangement and materials without departingfrom the scope of the invention as defined in the following claims.

We claim:

1. A hydraulic fuse comprising a cylinder, an aligned concentric chamberof a diameter larger than the cylinder, an inlet cap on the chamber, anoutlet cap on the cylinder, a valve seat associated with said outletcap, an axially bored valve member freely slidable in the cylinder andadapted to engage said seat, a peripheral flange on the inner end of thevalve member and slidably fitting the wall of the chamber, meteringopenings through said flange, check means in the valve member beyond theflange to prevent fluid flow from the chamber to the bore of the valvemember but permitting reverse flow, said chamber being enlarged at itsend adjacent the cylinder to provide increased clearance for the flangeas the valve member approaches the valve seat, spring means forretracting the valve member when the pressure is equalized between thecylinder and the chamber, and registering ports in the outlet cap andvalve seat providing suflicient fluid discharge to lower the pressure inthe cylinder below that on the flange end of the valve member toovercome the retracting spring and cause the valve member to contact thevalve seat.

2. A hydraulic fuse comprising a cylinder, an aligned concentric chamberof a diameter larger than the cylinder and connected therewith by alaterally extending shoulder, an inlet cap on the chamber, an outlet capon the cylinder, a valve seat associated with said outlet cap, anaxially bored valve member freely slidable in the cylinder and adaptedto engage said seat, a peripheral flange on the inner end of the valvemember and slidably fitting the wall of the chamber, metering openingsthrough said flange, check means in the 55 valve member beyond theflange to prevent fluid flow from the chamber to the bore of the valvemember but permitting reverse flow, said chamber being enlarged at itsend adjacent the laterally extending shoulder to provide increasedclearance for the flange as the valve member approaches the valve seat,compressible spring means between the laterally extending shoulder andthe flange, and registering ports in the outlet cap and valve seatproviding sufficient fluid discharge to lower the pressure in thecylinder below that on the flange end of the valve member to overcomesaid spring and cause the valve member to contact the valve seat.

3. A hydraulic fuse comprising a cylinder, an aligned concentric chamberof a diameter larger than the cylinder, an inlet cap on the chamber, anoutlet cap on the cylinder, a valve seat associated with said outletcap, an axially bored valve member freely slidable in the cylinder andadapted to engage said seat, a peripheral flange 0n the inner end of thevalve member and slidably fitting the wall of the chamber, meteringopenings through said flange, ball check valves disposed radially of thevalve member beyond the flange, a split ring retainer for the balls ofthe check valves, said chamber being enlarged at its end adjacent thecylinder to provide increased clearance for the flange as the valvemember approaches the valve seat, spring means for retracting the valvemember when the pressure is equalized between the cylinder and thechamber, and registering ports in the outlet cap and valve seatproviding suflicient fluid discharge to lower the pressure in thecylinder below that on the flange end of the valve member to overcomethe retracting spring and cause the valve member to contact the valveseat.

EMMETT C. HARTLEY.

HARRY B. CARBON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

